.TH std::binary_negate 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::binary_negate \- std::binary_negate

.SH Synopsis
   Defined in header <functional>
   template< class Predicate >

   struct binary_negate
       : public std::binary_function<
           Predicate::first_argument_type,   \fI(until C++11)\fP
           Predicate::second_argument_type,
           bool

       >;
   template< class Predicate >               \fI(since C++11)\fP
   struct binary_negate;                     (deprecated in C++17)
                                             (removed in C++20)

   std::binary_negate is a wrapper function object returning the complement of the
   binary predicate it holds.

   The binary predicate type must define two member types, first_argument_type and
   second_argument_type, that are convertible to the predicate's parameter types. The
   function objects obtained from std::owner_less, std::ref, std::cref, std::plus,
   std::minus, std::multiplies, std::divides, std::modulus, std::equal_to,
   std::not_equal_to, std::greater, std::less, std::greater_equal, std::less_equal,
   std::logical_not, std::logical_or, std::bit_and, std::bit_or, std::bit_xor,
   std::mem_fn, std::map::value_comp, std::multimap::value_comp, std::function, or from
   a call to std::not2 have these types defined, as are function objects derived from
   the deprecated std::binary_function.

   std::binary_negate objects are easily constructed with helper function std::not2.

.SH Member types

   Type                 Definition
   first_argument_type  Predicate::first_argument_type
   second_argument_type Predicate::second_argument_type
   result_type          bool

.SH Member functions

   constructor   constructs a new binary_negate object with the supplied predicate
                 \fI(public member function)\fP
                 returns the logical complement of the result of a call to the stored
   operator()    predicate
                 \fI(public member function)\fP

std::binary_negate::binary_negate

   explicit binary_negate( Predicate const& pred );            \fI(until C++14)\fP
   constexpr explicit binary_negate( Predicate const& pred );  \fI(since C++14)\fP

   Constructs a std::binary_negate function object with the stored predicate pred.

.SH Parameters

   pred - predicate function object

std::binary_negate::operator()

   bool operator()( first_argument_type const& x,                     \fI(until C++14)\fP
                    second_argument_type const& y ) const;
   constexpr bool operator()( first_argument_type const& x,           \fI(since C++14)\fP
                              second_argument_type const& y ) const;

   Returns the logical complement of the result of calling pred(x, y).

.SH Parameters

   x - first argument to pass through to predicate
   y - second argument to pass through to predicate

.SH Return value

   The logical complement of the result of calling pred(x, y).

.SH Example


// Run this code

 #include <algorithm>
 #include <cstddef>
 #include <functional>
 #include <iostream>
 #include <vector>

 struct same : std::binary_function<int, int, bool>
 {
     bool operator()(int a, int b) const { return a == b; }
 };

 int main()
 {
     std::vector<int> v1;
     for (int i = 0; i < 7; ++i)
         v1.push_back(i);

     std::vector<int> v2(v1.size());
     std::reverse_copy(v1.begin(), v1.end(), v2.begin());

     std::vector<bool> v3(v1.size());

     std::binary_negate<same> not_same((same()));

     // C++11 solution:
     // std::function<bool (int, int)> not_same =
     //     [](int x, int y) -> bool { return !same()(x, y); };

     std::transform(v1.begin(), v1.end(), v2.begin(), v3.begin(), not_same);

     std::cout.setf(std::ios_base::boolalpha);
     for (std::size_t i = 0; i != v1.size(); ++i)
         std::cout << v1[i] << " != " << v2[i] << " : " << v3[i] << '\\n';
 }

.SH Output:

 0 != 6 : true
 1 != 5 : true
 2 != 4 : true
 3 != 3 : false
 4 != 2 : true
 5 != 1 : true
 6 != 0 : true

.SH See also

   binary_function       adaptor-compatible binary function base class
   (deprecated in C++11) \fI(class template)\fP
   (removed in C++17)
   function              wraps callable object of any copy constructible type with
   \fI(C++11)\fP               specified function call signature
                         \fI(class template)\fP
   move_only_function    wraps callable object of any type with specified function call
   (C++23)               signature
                         \fI(class template)\fP
   not2                  constructs custom std::binary_negate object
   (deprecated in C++17) \fI(function template)\fP
   (removed in C++20)
   ptr_fun               creates an adaptor-compatible function object wrapper from a
   (deprecated in C++11) pointer to function
   (removed in C++17)    \fI(function template)\fP
   unary_negate          wrapper function object returning the complement of the unary
   (deprecated in C++17) predicate it holds
   (removed in C++20)    \fI(class template)\fP
